samer@32: %  specgrm - Time-Varying Spectrum
samer@32: % 
samer@32: %  specgrm ::
samer@32: %     X:[[T]]   ~'signal of length T',
samer@32: %     N:natural | H:[[N]] ~'window length or window', 
samer@32: %     M:natural ~'hop size',
samer@32: %     options {
samer@42: %		   fs :: nonneg/1	~'sampling rate';
samer@42: %      range:: [[2]] ~'range for tfdimage'
samer@32: %     }
samer@32: %  -> [[1+N/2,floor(T/M)]] ~'sequence of short term spectra'.  
samer@32: %
samer@32: %  Examples:
samer@32: %     Y1=specgram(x,hanning(256),128,'fs',44100)
samer@32: %
samer@32: %  Side Effects
samer@32: %    Image Plot of the spectrogram if no output
samer@32: 
samer@32: function y=specgrm(x,w,m,varargin)
samer@32: 	if length(w)==1,	H=ones(w,1); 
samer@32: 	else H=w; end
samer@32: 	if nargin<3 m=[]; end
samer@32: 	
samer@32: 	n = length(H); if isempty(m), m=n/2; end
samer@32: 	if n>m, bufargs={'nodelay'}; else bufargs={}; end
samer@32: 	y = powspec(diag(sparse(H))*buffer(zeropad(n-m,x),n,n-m,bufargs{:}));
samer@32: 
samer@32: 	% Make Spectrogram Display if no arg out
samer@32: 	if nargout==0
samer@42: 		opts=options('fs',1,'range',13.5,varargin{:});
samer@42: 
samer@43: 		tfdimage(y,n,m,opts.fs,opts.range,opts);
samer@32: 		clear y;
samer@32: 	end
samer@32: 
samer@32: